But he's...

Absolutely then the carb needs tuning, unless he's willing to settle for whatever minimally acceptable performance and mileage an out-of-the-box carburetor might give.

 

I agree. It is tough to tune a carb without an O2 sensor, but you can get it close. I'd start with tuning WOT...because it is the easiest. Jet up and down to see what it likes...but don't stop there! The jets aren't the proper way to tune WOT. You need to resize the PVCR passages appropriately. My last carb wanted 7 jet sizes more for best performance at WOT. I drilled out my primary PVCR's .006" and dropped the jets back down to stock size (i believe they were 70's). Now, I can cruise with a lean mixture but still have proper AFR for those WOT blasts down the 1/4 mile.

 

Oh i agree it can ues a little tweek here and there. As for an 02 sensor, if the car still has the computer in it but the carb is non CC I dont see what any good a 02 sensor will do.

 

Don't worry, you don't need an O2 sensor to tune it.

 

Oh I knew that, it was the comment by pancherj, that had me thring to figure out how to tune it with one. Holleys are easy to tune so he should have no problems.

 

WOT is easy to tune without an O2 sensor (at the track). Tuning the transition, IAB's, HSAB's for all driving conditions is a bit harder. Even with an O2 sensor, everything is a compromise. Can you bolt a carb on, change some jets and go? Sure. Is that best? No way. I am still learning, but it has been an eye opening experience. My last carb tuning was with a 3310. I upped the jets and lowered the vacuum secondary spring (to make it open quicker). I thought that was tuning!

 

I agree with you, however for a daily driver tuning it for the track give you only a tune for the track. for a daily driver there are a few things that can be done to improve streetablity and get something for the track. Jetting is fine he can go up or down a size or two, change the power valve to open a little later and change the acc pump on the primary side. it is a trial and error thing.

 

Very true and well said. I don't drive my car as much anymore (mostly race). It is definitely a compromise between racing and street driving. My experience with Holley's is that they are way too rich at low speed/low throttle opening. For a street car, I would concentrate on that area most.

 

This is were mechanical secondaries comes into play on a holley. this way you dont have to rely on a vaumn unit to open the rear. with a mech secondary you can set it to were you want it to open. On an older 750 I ran years ago on a built 350 I put a very little nut and bolt on the rear of the carb were the rod for the secondaies are, so when I hit it a little past half way they would snap open. and with a little tweek on the jet size it never flooded or hesitated. Instant WOT. it was great for a rolling start. and took a while to get used to it for a dead stop run.